PROJECT SUMMARY/ABSTRACT ? Research Project 1 Ebola virus (EBOV) and Marburg virus (MARV) are filamentous enveloped non-segmented negative sense RNA viruses representing the two genera that comprise the family Filoviridae. The Marburgvirus genus contains one species (MARV), while the Ebolavirus genus is comprised of five recognized species: Sudan ebolavirus (SUDV), Zaire ebolavirus (EBOV), Tai Forest ebolavirus (TAFV), Reston ebolavirus (RESTV), and Bundibugyo ebolavirus (BDBV). These viruses are important human pathogens with case fatality rates ranging from 70% to 90% for EBOV, up to 90% for MARV, approximately 55% for SUDV, and 25-50% for BDBV. These agents are classified as Category A Priority Pathogens by the NIAID/NIH and CDC, and there are presently no licensed active or passive interventions for exposure resulting from natural outbreak, laboratory accident, or deliberate misuse. The public health concern is based on both the emerging infectious disease status of these viruses and their potential use as biologic weapons. An effective prophylactic vaccine would find application with medical personnel and close contacts during outbreaks in endemic areas of sub-Saharan Africa, with laboratory workers engaged in filovirus research, and with military and civilian personnel threatened by weaponized filoviruses. The ideal vaccine to meet both the outbreak and bioweapon scenarios would rapidly confer protection against all species of EBOV and MARV with a single dose. Among the vaccine strategies tested for single dose protection, the most successful have been vectored vaccines based on vesicular stomatitis virus (VSV). The progressing urbanization of sub-Saharan Africa has increased the probability that a filovirus infected individual will enter an area of high population density either unknowingly or to seek medical aid. As seen in the recent west African outbreak, the increased mobility within and between the urban centers can rapidly expand the number and geographic distribution of cases. Thus, in the absence of widespread prophylactic immunization, the most effective uses of a vaccine against the filoviruses will be protection of healthcare workers and breaking spread using `ring vaccination'. The first application is aided by, and the second application is dependent upon, a rapid onset of protection. Funded work under NIAID contract HHSN272201700077C supports development of vaccines for EBOV, SUDV, and MARV that are vectored with rVSVN4CT1, a live attenuated VSV vector that has proven safe in multiple clinical trials. This application proposes to develop an rVSVN4CT1-vectored BDBV vaccine through MVS production and IND-enabling toxicology testing, to establish the time to onset of protection provided by rVSVN4CT1-vectored vaccines against the four filovirus species of greatest concern (EBOV, SUDV, BDBV, and MARV). In addition, it proposes to address the questions regarding the vaccine valency providing the most effective formulation for use in a rapid response setting.